The present disclosure is related to the electronic monitoring of fuses, that is, the indication of fuse blowout. Often a blown-out fuse can be noticed quickly by techniques other than through visual inspection of fuses, and in automation systems especially the information on a blown-out fuse can be transmitted automatically.
Some handle-type fuse models include a component which protrudes when the fuse blows out and it can be arranged to transmit the mechanical contact information. However, this is not possible with most fuses, in which case, the condition of the fuse should be assessed by measuring the voltage after the fuse, or current running through the fuse.
In order to recognise a blown-out fuse in an arrangement utilising current measurement, the circuit load is switched on. Alternatively, the voltage can be measured over the fuse, which is in practice 0V with an undamaged fuse. With a blown-out fuse the voltage over the fuse is almost similar to the supply voltage, assuming that the load is switched on.
CN 201274274 Y introduces a fuse monitoring coupling in which an LED controlled by a transistor indicates that the fuse has blown. Such couplings are suitable for circuits with very low voltages and, additionally, the sizing of components is such that the voltage should be relatively stable.
In some applications it is desired that the fuse guard indicates the condition of fuses both in the positive and negative poles of the DC voltage supply. An additional specification may be that the fuse guard can be applied to a very wide range of rated supply voltages or, at least, it should allow even large voltage variations in the supply voltage circuit.